It seems like France was allowed to stay as a key player in European politics at the time, even after the French had just invaded most of Europe. They were even allowed to use their army to help put down rebellions in Spain not long afterwards. While I understand that they were working as part of an alliance system to maintain the European balance of power, it seems like the rest of Europe was very lenient. Did France have any fines or restrictions put in place for a certain amount of time?
I recently finished reading a book about this. Basically the Coalition was fighting to remove the "usurper", our friend Napoleon, and restore the "rightful monarch", our slightly obese friend Louis XVIII. But even the Coalition was divided about this, as the British were staunchly fighting to restore the Bourbons yet the Prussians wanted revenge for what France had done to Prussia a decade prior.
So as you can see, it was a pretty complicated situation. Borders were restored to Bourbon pre-Napoleon/Revolution times, the Kingdom of the Netherlands was established as a strong player to act as a buffer against France in the years to come.
The biggest punishment I can think of is the allied occupation of France, as both British/Dutch and Prussian armies occupied parts of France after Waterloo. And their approach was very different as well, Wellington had his troops behave like they were guests of King Louis XVIII, keeping the peace in his kingdom. But the Prussians were acting as a proper occupier, looting and attempting to destroy as many Napoleon artifacts as possible. One notorious example is a bridge in Paris, which the Prussians were hellbent on destroying but Wellington stationed British troops on it to avoid them blowing it up.
To end it in short: France got the "soft treatment" because it the Bourbons were the rightful monarchs according to the British, France had merely been enslaved under the tyranny of Bonaparte as they put it. Prussians disagreed yet respected the size of the now restored Bourbon France.
Source: Waterloo - 200 jaar strijd, de Jong, J., Schoenmaker, B., van Zanten, J., 2015.
France had to pay an indemnity of 700 million francs (about a month's GDP) and host an Allied occupation force, which was withdrawn in 1818. The provisions were generally lenient because both the Republican and Napoleonic regimes were gone, to be replaced by the restored Bourbons whom the Allies viewed favourably, soon accepting them into their ranks.