I was wondering whether it is all ready possible to install a program to the harddisk while running Antix live from USB (in non-persistence mode). I'm not sure whether it is all ready possible since to the best of my knowledge, install locations for programs can't be selected, and they may also alter files in folders of the operating system.

The idea is that this way, the Antix OS on the USB stick doesn't get altered (which is beneficial as for example in MS Windows adding and removing programs corrupted the registry over time). It also keeps the USB stick mobile and sleek. By inserting the USB stick on different PC's (on which the harddisks have different programs on them, one can use the PC's he owner has at home more effectively (and not get slowed down by needing to find/wade trough many programs, some of which for a given task are not needed (PC's can then be used for specific tasks -say video editing, graphic work, internet use, ...).

I assume that Antix will need to get a specific text file it will need to load on boot telling it where to find the programs (harddisk location), ie if started using shortcuts. Alternatively, and peerhaps easier, the programs can be started manually by opening the location on the harddisk using a file browser. The only real difficulty I see is that folders of the operating system itself may be changed, and that the program install location may not be chosen by the user.

The idea would be combinable with the ideas at viewtopic.php?f=49&t=5292

I don't know about actually installing files, but you could a put a persistence file on the local hard drive and keep the usb running the base"live". if you gave all the PC hard drive partitions the same label, you could set the boot loader on the usb to search for the persistence file on devices with the given label. This is really easy in MX and in the new antiX-14, but I think the capability is there in 13.2 just not as automated. In other words, you'll have to make your own boot entry.