Even though it's not really blob but a lot of .jar files, they are still pre-compiled files. As far as I know pycharm-community is FLOSS and available at https://github.com/JetBrains/intellij-community/tree/master/python therefore the ebuild should build it from sources.
Agreed. I invite everybody to contribute a working ebuild. I don't have the ressources at hand to look into it, right now.
I have neither time nor capacity to support this now, Although I have heard that one of gentoo devs maintains source buld in their overlay (ikelos).