This appears to be no longer available. The link redirects to siraudiotools' products page, where you can buy SIR2. There is no entry for (free) SIR1.
@Thohi It's too slow to calculate convolution without latency. The only way to do it without latency is fully in the time domain, where each sample of output requires /n/ multiply-and-add operations (/n/ being the size of the convolution kernel). It's actually faster to FFT the input, multiply by the IR spectrum, and IFFT to get the output... but you have to collect an entire FFT frame's worth of audio before you can do that, hence the latency.