Hello! Sorry to bug about an old unsupported version. I just wanted to ask if you could add functionality to this line in HarvestBlockHandler.java so it allowed plant fibers to drop from anything in the ore:grass oreDict.

If you won't, can you advise me on what I could do if I cloned and added the code myself. Would that violate the license you're using if I distributed that modified version in a modpack? Sorry if this is a stupid question.

an old unsupported version

old unsupported versions are by definition unsupported, and so no, I will not be supporting this old version.

I suggest you read the license (my bold):

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.