It might be a bit late but I think it is worth to mention that you can professionally scrape Google reliable and not cause problems with it.
Actually it is not of any threat I know about to scrape Google.
It is cahllenging if you are unexperienced but I am not aware about a single case of legal consequence and I am always following this topic.
Maybe one of the largest cases of scraping happened some years ago when Microsoft scraped Google to power Bing. Google was able to proof it by placing fake results which do not exist in real world and Bing suddenly took them up.
Google named and shamed them, that's all that happened as far as I remember.
Using the API is rarely ever a real use, it costs a lot of money to use it for even a small amount of results and the free amount is rather small (40 lookups per hour before ban).
The other downside is that the API does not mirror the real search results, in your case maybe less a problem but in most cases people want to get the real ranking positions.
Now if you do not accept Googles TOS or ignore it (they did not care about your TOS when they scraped you in their startup) you can go another route.
Mimic a real user and get the data directly from the SERPs.
The clue here is to send around 10 requests per hour (can be increased to 20) with each IP address (yes you use more than one IP). That amount has proven to cause no problem with Google over the past years.
Use caching, databases, ip rotation management to avoid hitting it more often than required.
The IP addresses need to be clean, unshared and if possible without abusive history.
The originally suggested proxy-list would complicate the topic a lot as you receive unstable, unreliable IPs with questionable absuive use, share and history.
There is an open source PHP project on http://scraping.compunect.com which contains all the features you need to start, I used it for my work which now runs for some years without troubles.
Thats a finished project which is mainly built to be used as customizable base of your project but runs standalone too.
Also PHP is not a bad choice, I originally was sceptical but I was running PHP (5) as background process for two years without a single interruption.
The performance is easily good enough for such a project so I would give it a shot.
Otherwise, PHP code is like C/JAVA .. you can see how things are done and repeat them in your own project.