Whenever I see such an offer, I'll try to turn the software in a portable version. Most of the time that works, sometimes it doesn't. But lately I didn't see much that was interesting to me at GAOTD, so I didn't bother.
Buying stuff on the internet without having a credit card is quite problematic. But I don't want one, because I don't like the concept behind it. A debit card is much more to my liking, but very unpopular with banks and vendors alike. When living in the Netherlands I did have a bank card and that I used a lot, because it felt much more secure than a credit card. Just saying, it's not that I have too much against 'plastic', I just don't like credit cards.
Besides that, banks here in Paraguay are expensive. Much more so than in the US or the Netherlands and therefore a lot of cooperativa's are formed that handle money from people. For example, banks charge interest of 23% (legal limit, else it would be higher) on any amount their customer borrows. Taking in account the exchange rate, you also need to keep minimum of about 1500 USD permanently in your bank account. Most people make 250-300USD per month, so a lot of people can't afford a bank, even if they wanted to. Only banks give out credit cards, so getting one is near impossible here in Paraguay.
If you do have one, you can pay practically everywhere with it, it is not that Paraguay is that much of a backwater. It is just that this economy is very much cash-oriented. Buying things in parcels is also very popular here and although people don't speak English here, almost anyone does understand (and like) you when you say "I pay cash on the dash" to them.