Details of the scenario you try and problem that is occurring:
When PowerShell 4,0 is installed calling Invoke-Sqlcmd from the helper function Invoke-SqlScript fails.
See more detailed explanation here:
#252 (comment)

If there is no solution to running this resource using PowerShell 4.0, then as a minimum we have to document in the README.md that this is PowerShell 5.0 only.

The DSC configuration that is using the resource (as detailed as possible):
Configuration

xSQLServerScript 'SQL2014-RunSQLScript'
{
    ServerInstance = 'sqltest3.company.local\SQL2014'
    SetFilePath = 'C:\DSCTemp\SQLScripts\Set-RunSQLScript.sql'
    TestFilePath = 'C:\DSCTemp\SQLScripts\Test-RunSQLScript.sql'
    GetFilePath = 'C:\DSCTemp\SQLScripts\Get-RunSQLScript.sql'
}  

Get-RunSQLScript.sql

select name from sys.databases where name = 'MyScriptDatabase1'

Set-RunSQLScript.sql

CREATE DATABASE [MyScriptDatabase1]

Test-RunSQLScript.sql

if (select count(name) from sys.databases where name = 'MyScriptDatabase1') = 0
BEGIN
	RAISERROR ('Did not find database [MyScriptDatabase1]', 16, 1)
END
ELSE
BEGIN
	PRINT 'Found database [MyScriptDatabase1]'
END

Version of the Operating System, SQL Server and PowerShell the DSC Target Node is running:
Windows Server 2012 R2, SQL Server 2014, PowerShell 4.0

Version of the DSC module you're using, or 'dev' if you're using current dev branch:
Dev