The source of the old, free notecase version is here. libgtksourceview2.0-0 is needed.

After downloading I tried to run make and got an error.

===> Linking bin/notecase
/usr/bin/ld: ./bin/eggtrayicon.o: undefined reference to symbol 'XFlush'
//usr/lib/i386-linux-gnu/libX11.so.6: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
Makefile:319: die Regel für Ziel „bin/notecase“ scheiterte
make: *** [bin/notecase] Fehler 1

After running make "LDFLAGS=-lX11" the binary was linked.