You can absolutely share Studio 5 lbs files on GitHub. The advantage of using Studio 8.1 is that you can also dump the source to readable files, then use git to compare and manage the code. I recommend you:
1. Post the Studio 5 lbs file(s) so others can download and use them
2. Update a local copy of the library to Studio 8.1
3. Export the source from 8.1
4. Include that source with your Studio 5 library
If someone wants to offer an enhancement with a pull request, have them do the same. That way you, and others, can compare and see the differences in the exported code. Studio 8.1 doesn’t radically change code from 5, so reviewing the exported 8.1 code should give you a fair evaluation of what’s changed in Studio 5.