How to run k-meleon of different versions concurrently ?

Depending on what subdirectory you would have installed, for at least the 1.5 series your shortcut for starting it would be something like:
"C:\Program Files\K-Meleon1.5a2\k-meleon.exe" -new

It is not possible to have two instances of K-Meleon
opened at the same time, be that of the same version
or of different versions.
But you can of course have different versions on your
computer and use them alternatively, but preferrably
with different profiles.
Only one version should use a multiuser profile in the
central applications folder.
Additional versions should get their own profile
inside the K-Meleon main directory.
To achieve the creation of this additional profile,
a file profile.ini has to be present in the K-Meleon
root (main) directory, which initiates this process.
This profile.ini is usually always present in alpha
or beta versions, or also in unofficial variations
of the browser.
If this should not be the case, you can add yourself
a file profile.ini into the K-Meleon root directory
before the first start of the browser.
Open notepad and create a file containing only the lines :

[profile]
path=profiles
IsRelative=1

Save it as profile.ini, as "All files", not as .txt .
The ending must be .ini, not .ini.txt .

For official browser updates, the central profile
in the users application folder can be reused usually.

Fred

Thanks, Fred, should have mentioned about localization through the .ini file. That having been said, you can in fact have two instances of the 1.5 series running simultaneously. I can use both build 22 and build 23 simultaneously. Each is stored in its own subdirectory with its own profile.

The trick is using the -new in running them from a shortcut:
build 22 is invoked: "C:\Program Files\K-Meleon1.5\k-meleon.exe" -new
build 23 is invoked: "C:\Program Files\K-Meleon1.5a2\k-meleon.exe" -new

As you said, these are not multi-user but run locally using profile.ini.

Thank you, Terry for correcting me.
These command line options are a new possibility, and
I missed the information about that. These options were
not available before.
More precise info can be read here :

http://kmeleon.sourceforge.net/wiki/CommandLineOptions

But we must point out that these command line options
work only for versions of K-Meleon 1.1 and higher.
That means versions 1.0.x , 0.9.x and their variations
that use the older macro structure will not accept
more than one instance at the same time.

Fred

Thank you for the info!

With the -new commandline option, I can only run 2 instances at max.

The third one start and exit immediately.

Ignore my previous post please. Something wrong with my computer.

Yes, with the -new and different profiles, I can run any number of instances.