What are some alternatives?
When comparing MKVToolnix and MP4Joiner, you can also consider the following products
FFmpeg - Open source multimedia suite for conversion, playback, profiling, and streaming.
Boilsoft Video Joiner - Boilsoft Video Joiner is a powerful video merger to join AVI, MPEG, MPG, VOB, RM/RMVB, 3GP, ASF, WMV, WMA, MP4, MP4A, MKV or FLV files, and so forth.
Subler - Subler is a Mac OS X application that opens media containers, allows you to add or remove media...
MKVExtractGUI - This is a GUI frontend for mkvextract from ...
gMKVExtractGUI - GUI front-end for mkvinfo and mkvextract CLI tools.
HandBrake - HandBrake allows users to easily convert video files into a wide variety of different formats.