I do not see in the warranty anywhere that it says the warranty is voided if you change the OS..
It does say:
They don't warrant the installed software.
They are not responsible for the installed software
They are not responsible for loss of your data
They are not responsible for damage caused by software (viruses, etc)
Forcing me to use the Linpus interface for a year in order to not void a warranty, would be a punishment far worse than having to pay for a product repair imho.. but maybe that's just me.
Good luck, I've found almost no information on the Linpus OS.. their website is sorely lacking in documentation.