As you can see, the light effects behave exactly like in RMXVA. There are only 2 things to consider. I have written them already down in the script for you so I'll just copy-paste it here.
Quote#==============================================================================
#
# Configuration:
#
# Due to the difference in the mapping systems between RMXP and RMVXA, the way
# walls and roofs work in RMXVA cannot be reproduced completely in RMXP.
# Instead of this, a few additional terrain tags have to be configured.
#
# L_Wall_Tag - terrain tag for left wall end
# R_Wall_Tag - terrain tag for right wall end
# L_Roof_Tag - terrain tag for left roof end
# R_Roof_Tag - terrain tag for right roof end
#
#==============================================================================
#
# Notes:
#
# Because RMXP and RMVXA use different types of tilesets, make sure you have a
# tileset that works well with RMXP. RMVXA's tilesets are based on square
# objects that take up a whole tile while RMXP is based on tiles that can
# contain partial graphic elements that are combined into a larger element on
# the final map. e.g. RMXP's walls has rounded edges.
#
#::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Let me know if you are satisfied with the results, because honestly, I'm not that satisfied. ._. While the script is pretty cool and all, RMXP's tilesets just weren't made for something like this. But if you use custom tilesets, you will have no problems. The only other problem that I noticed is lag, but RMXP has problems with that by default so yeah.
I give you a simple warranty on this script: If something doesn't work or there is a bug, I will fix it free of charge. Other than that, the script is "as is" and I take no responsibility in how you use it.
Once you transfer the money, I will PM (or email, whichever you prefer) you the script with the demo. It comes in 2 parts, one of which goes above the original script and the other one below. The original script itself stays unaltered that way.
My PayPal email is boris[dot]blizzard[at]gmail[dot]com.