I am just starting with OpenProject for my site eggsh.com that is being used to design software available for free under the Apache license. I'd like to have a custom theme to make the site more compatible with my website and I understand that the Enterprise Edition makes this possible.

But, the Enterprise edition requires a minimum of 20 users, and we are just two or maybe three people. Also, we are working not doing this work for profit and the code we create is available for free. So, the cost of an Enterprise subscription is not something we can do.

Are there free or more affordable options that are available for customization of the site for small non-profits like us?