No, you are not gambling because gambling means betting money for the prospects of more money in a chance game. Since those prospects don't exist here, it's not actual gambling, just a theatrical simulation of such. This is as much gambling as playing poker with bean seeds with your church friends, or better yet, buying a "cassino games" pc game that doesn't involve real betting, which exist by the hundreds and are perfectly legal and have long been in many countries where gambling is prohibited.
This is tending towards policy discussion, but many jurisdictions don't define gambling solely in terms of monetary payout. A game of chance that takes some form of value payment for the the possibility of winning something to which value can be assigned can be considered gambling even if the winnings aren't in cash.
Otherwise, a casino that has winnings in non-cash items goods or services would readily skirt regulations on gambling. Similarly, tax authorities would take a dim view of saying non-cash payouts have zero monetary value for the purposes of taxation.
A raffle that gives away movie tickets would have winnings that would be evaluated in terms of the value assigned to the tickets, either in retail price or what the market has assigned to them. An ostensibly inexpensive ticket for a high-demand show that might have high value in an auction might be evaluated in terms of the higher amount, and making prizes in the form of digital content or services would invite analysis in terms of what people pay for them.
In this regard, an online casino may still invite scrutiny, if whatever is used to pay into and out of the casino can be used to procure items that people clearly place a value upon--more so if the online currency is an intermediate item that can be bought with cash (otherwise, poker chips would be an exploitable loophole). If the online currency can be bought with real money, and the payout from the casino can be used in the same way as whatever is bought with real money, there's a potential way to view these winnings as having a tacit form of value even if they cannot be cashed out directly. Other games or publishers have made similar tacit admissions (paying for gold farming in WoW, the stated reasoning for the real-money auction house in Diablo 3, the statements by publishers about their goal of establishing "value" in the minds of gamers to keep them engaged and spending).
A developer's say-so isn't the only arbiter on whether value can be assigned, and since MMO games like GTA and others explicitly recognize a system of values and transfer of value that they call an "economy" that they actively manage and allow real cash to flow into, there's a recognition that there is at least one "something" that people are willing to pay real money for inside the game, and if it shares a means of exchange with a game of chance there's a link that might be somewhat indirect--but not more so than many historical attempts at evading the law that have historically been shut down.
It can be argued that since online money can be made in-game that there isn't a 1:1 correspondence, or that the valuation can be obfuscated, but the actions Rockstar takes to maintain its online currency by adjusting item prices in updates and patching/punishing money duplication exploits in order to maintain its own profiting from the artificial economy indicate that the real-money worth of what is being gambled is substantially non-zero.
Whether a given area's regulations are written to capture this specific electronic scenario may vary, but the link between real-world value and what is being yielded from the games of chance seems like it has various analogues to other ways gaming establishments tried to skirt regulation or law enforcement scrutiny.
