Sure - Tcl of course kept all the contributions that Sun made. However, when the wind from Sun went out of Tcl's sails, it slowed down a lot.

true - hopefully that won't happen here - seems to be more outside influence for sure.

At least one of the JRuby committers (Ola Bini) is working for Thoughtworks. So even if Sun dropped JRuby, other companies would probably take up the slack as in this case.

JRuby makes sense in terms of enterprise software/consulting as well and probably doesn't need sun's upport to survive and even thrive (though of course Sun's support is a huge positive).