ftp://novix.oih.rwth-aachen.de/pub/ntba.zip (ca. 170kB)
No, that's not possible. The concept of ISDN doesn't allow it. A NTBA or a PBX with an internal bus is required.
Yes. Both ISDN packages load the module isdn.o, otherwise the naming conventions are different. Tip: rename Urlichs isdn.o to uisdn.o, and change lib/modules/modules.isdn (or whatever the file is called that lists the modules and is read by the script) accordingly. Happily the default names of the ISDN devices are also different.