Grounding JTAG Lines
Grounding the JTAG input lines (TCK, TMS, and TDI) is fine, although it'll make the port unusable. The JTAG output, TDO, is another matter — grounding it will cause a short circuit if it is driven high by the CPLD! If you cannot bring JTAG out to a dedicated set of pins, you're probably best off leaving it disconnected.