Quick Guide to Custom Firmware (click)
No you don't, you only need to clear the protection flag. The DLNA service you are using decrypts on the fly - but only if [1] the recording is not protected (ie a StDef recording, or a HiDef recording that has had the protection flag cleared), or [2] the DLNA client negotiates DTCP (we've not found anything that can do this other than another HDR-FOX or HD-FOX, or maybe one of the other Humax PVRs). See the
auto-unprotect package.
Custom Firmware users generally decrypt all recordings by routine anyway, as that opens the way to unrestricted use of the recordings - not just DLNA.
Decryption Guide (click)
The media players built into TVs are generally not compatible with the M2TS format of the recording files (even though they are named .ts).