The GPL allows you to modify the source and provide a service on a public server without having to share your modifications.* But I understand if you prefer a

The GPL allows you to modify the source and provide a service on a public server without having to share your modifications.* But I understand if you prefer a more permissíve license. Lots of people go with MIT License, it's very short, permissive and compatible with the GPL. Apache v2 is also compatible. See here about EPL being incompatible: https://www.fsf.org/blogs/licensing/using-the-gpl-for-eclipse-plug-ins https://www.fsf.org/blogs/licensing/using-the-gpl-for-eclips... Last time I tried understanding the key subtleties of the EPL I came out empty handed, but it would seem it's more viral than the permissive licenses above, bit less so than the GPL. * That's why the AGPL exists, so someone working on a Lux REPL would only have to show the code for his online Lux modifications if Lux was AGPL.