It is a tough feeling to see someone else's design for a library that would be literally perfect for my needs, but I'm unable to use it because of the license, so I have to spend weeks implementing my own inferior version while carefully avoiding making the code too similar to what I happen to remember. I'm past believing that I'm smart enough to always be able to come up with/reimplement a competent enough solution…
Curious, what license(s) prevented you from using a library? Or maybe rather, what does "use" mean here?
"Use" in this case means to have some feature that's implemented by those libraries reimplemented in an open-source project (MIT-licensed).