This means that if you distribute your dissector, you have to make your sources available.

This is nothing new though: all wireshark plugins must be GPL, since the API itself they rely on is GPL.

v3 means that if it's used (even over a network) by somebody, they can request the code, versus GPLv2 (Wireshark license), which says if you distribute binaries of Wireshark or software based on it, you must provide the source. The difference is that you could theoretically provide a web interface to a GPLv2 project and not need to supply the source, but if you provide such an interface to GPLv3 software, you could receive a request for the code.

EDIT: I'm not entirely correct There are provisions for the network situation ("ASP (application service provider) loophole") I described, but I looks like it's not necessarily the default mode. See [0][1].

[0] https://en.wikipedia.org/wiki/GNU_General_Public_License

[1] https://en.wikipedia.org/wiki/Affero_General_Public_License

Nop The 'over the network' stuff is AGPL

The GNU GPL v3 does not contain such a provision. However, a different license, the GNU AGPL v3, does. Your post is entirely incorrect regarding the GPLv3.

As Wikipedia notes, some drafts of the GPLv3 contained such a provision, but this did not make it into the final version.

Only if you release it.