The plugins were made a long time ago (in 4.2 or 4.3 I think).
Initially I made them to support my own games, since the games that I wanted to make weren’t possible with just blueprint alone, and I really didn’t want to be bothered with C++ because it’s slow to compile, it’s slow to get the intellisense info, it has a very high risk of memory problems, etc.
Later I noticed that the plugins were actually quite useful for about any project really.
Then I thought that perhaps I could sell them, to get some of the time/money back that I had to put into it.
The plugins were somewhat done already about 11-12 months ago (they were still in a very rough/beta-ish state back then though, the plugins have matured a lot since then).
Anyway, the thing is though, Epic’s code plugin marketplace system wasn’t done yet back then, so it was impossible to have code plugins on the marketplace at that time.
Code plugins on the marketplace just recently became possible, which is why the Low Entry plugins just recently became available on the marketplace.