No, the European model (ECMWF IFS) is not open source, and they don't even release most of the operational forecast data that they produce to the general public. As far as I know the UK and others don't either.
(Disclaimer: I don't work in operational modeling)
NOAA just upgraded last year to a system that hits 8.4 petaflops, which is about the same as the European system, and the Japanese and UK systems are fairly similar.
More computing power would absolutely help the NOAA models (primarily GFS) increase resolution, improve the data assimilation method that generates the initial conditions, and increase the number of ensembles run. The GFS lags the European model in all of these areas. It would especially help increase the number of ensembles, since that is an embarrassingly parallel problem. However, NOAA also needs more researchers and funding. For example, model configuration changes not only need to be developed, but also tested to ensure that there aren't unexpected regressions in forecast skill. And, for example, the Europeans have put a lot of research and development into their data assimilation method, and it's one of the reasons they tend to outperform other models.
For all but the most extreme configurations, WRF will run on a modern 2-4 core Linux desktop. It will be fairly slow, but it will run.
You can use the raw data from the official model runs published by NOAA as initial and boundary conditions for your model runs: https://nomads.ncep.noaa.gov . One of the coolest and most under appreciated things about NOAA is that they publish everything online for free for everyone.
Or you can just get the raw data from the official runs from the link above and do your own extraction, and maybe post processing if you like.
(Source: PhD in meteorology. Finally made an account when I saw this posted)