Modifying and redistributing OFL fonts

What changes am I allowed to make to OFL fonts?

The OFL allows any types of modification. If you then redistribute that font to others you must include the original copyright statements, any Reserved Font Name (RFN) declarations, and the OFL license text. If there are RFNs you may also need to change the internal font names. See Managing Reserved Font Names (RFNs).

What tools and processes can I use?

Any tools you wish. There is no restriction on the methods or tools you can use to modify OFL fonts.

What do I need to do to redistribute a modified font?

The important basic steps are:

  • Make your modifications.
  • If the font has RFNs you may need to change the font name (both internal name fields and anything a user might see) to avoid using any RFNs. See Managing Reserved Font Names (RFNs).
  • Add your copyright info to the OFL.txt file and the Copyright field in the font, making it clear what you added. For example, if you added a Bold weight you could add a statement after the existing one, such as: “Bold glyphs copyright (c) year name”.
  • Declare any additional RFNs you wish to add to the font after the copyright statements.
  • Add an entry to the FONTLOG.txt file describing your contributions and changes.
  • Include the OFL.txt, OFL-FAQ.txt, and FONTLOG.txt files in your font release package.

This adds you as an additional copyright holder but also makes it clear that you have built upon the work of the original author(s).

What about charging for a modified font? Getting commissioned to extend an existing font?

You are welcome to charge for your expertise and your time, but be aware that you will not be able to just sell the font by itself and keep it exclusive to a single client. You are making changes to an existing open font and creating a derivative which means that new version must also remain open and should be publicly released.

Besides meeting your own needs, modifications to existing fonts under the OFL can be done for various reasons, including:

  • to extend the scope and feature set of a particular design project
  • to meet the needs of a specific language community
  • to add value to a product or service made by your own company or a company you work for
  • to meet the goals of a sponsoring organisation via a commissioned design

You may want to consider how crowdfunding or subscription-supported services could provide funds to extend a project for the benefit of more users.

Please also consider contributing your improvements to the original font project. Contact the original author or project maintainer for information on how to contribute.

Specific answers from the OFL-FAQ

The following questions and answers are color-coded to help make it easier to understand, but please do click on the question to reveal the answer and read through the details. This is only a small subset of the questions and answers available in the OFL-FAQ. Please read the full OFL-FAQ for in-depth information.

Green generally means yes. Red generally means no. Yellow means it depends on the situation. Blue means informational.

You are allowed to change anything, as long as such changes do not violate the terms of the license. In other words, you are not allowed to remove the copyright statement(s) from the font, but you could put additional information into it that covers your contribution. See the placeholders in the OFL header template for recommendations on where to add your own statements. (Remember that, when authors have reserved names via the RFN mechanism, you need to change the internal names of the font to your own font name when making your modified version even if it is just a small change.)
Not by itself. Derivative fonts must be released under the OFL and cannot be sold by themselves. It is permitted, however, to include them in a larger software package (such as text editors, office suites or operating systems), even if the larger package is sold. In that case, you are strongly encouraged, but not required, to also make that derived font easily and freely available outside of the larger package.
No, but please consider sharing your improvements with others. You may find that you receive in return more than what you gave.
These are font names, or portions of font names, that the author has chosen to reserve for use only with the Original Version of the font, or for Modified Version(s) created by the original author.
The best way to acknowledge the source of the design is to thank the original authors and any other contributors in the files that are distributed with your revised font (although no acknowledgement is required). The FONTLOG is a natural place to do this. Reserved Font Names ensure that the only fonts that have the original names are the unmodified Original Versions. This allows designers to maintain artistic integrity while allowing collaboration to happen. It eliminates potential confusion and name conflicts. When choosing a name, be creative and avoid names that reuse almost all the same letters in the same order or sound like the original. It will help everyone if Original Versions and Modified Versions can easily be distinguished from one another and from other derivatives. Any substitution and matching mechanism is outside the scope of the license.
The Copyright Holder(s) can give certain trusted parties the right to use any of the Reserved Font Names through separate written agreements. For example, even if “Foobar” is an RFN, you could write up an agreement to give company “XYZ” the right to distribute a modified version with a name that includes “Foobar”. This allows for freedom without confusion. The existence of such an agreement should be made as clear as possible to downstream users and designers in the distribution package and the relevant documentation. They need to know if they are a party to the agreement or not and what they are practically allowed to do or not even if all the details of the agreement are not public.
Yes, all rebuilds which change the font data and the smart code are Modified Versions and the requirements of the OFL apply: you need to respect what the Author(s) have chosen in terms of Reserved Font Names. However if a package (or installer) is simply a wrapper or a compressed structure around the final font - leaving them intact on the inside - then no name change is required. Please get in touch with the author(s) and copyright holder(s) to inquire about the presence of font sources beyond the final font file(s) and the recommended build path. That build path may very well be non-trivial and hard to reproduce accurately by the maintainer. If a full font build path is made available by the upstream author(s) please be aware that any regressions and changes you may introduce when doing a rebuild for packaging purposes is your responsibility as a package maintainer since you are effectively creating a separate branch. You should make it very clear to your users that your rebuilt version is not the canonical one from upstream.
In many cases, yes. It is common for OFL fonts to be developed by a team of people who welcome contributions from the wider community. Contact the original authors for specific information on how to participate in their projects.
Most authors would be very happy to receive such contributions. Keep in mind that it is unlikely that they would want to incorporate major changes that would require additional work on their end. Any contributions would likely need to be made for all the fonts in a family and match the overall design and style. Authors are encouraged to include a guide to the design with the fonts. It would also help to have contributions submitted as patches or clearly marked changes - the use of smart source revision control systems like subversion, mercurial, git or bzr is a good idea. Please follow the recommendations given by the author(s) in terms of preferred source formats and configuration parameters for sending contributions. If this is not indicated in a FONTLOG or other documentation of the font, consider asking them directly. Examples of useful contributions are bug fixes, additional glyphs, stylistic alternates (and the smart font code to access them) or improved hinting. Keep in mind that some kinds of changes (esp. hinting) may be technically difficult to integrate.