Is Geometry shader not work with GL3?

that's only the default shader if @gridmode is 0 (quadgrid). if you set @gridmode 0 on your gridshape that shader should work. for the default jit.gl.gridshape (@gridmode 1 - trigrid) this is the default shader:

<jittershader name="fill-flat-triangles">
    <description>
        An auto-generated shader for simulating deprecated OpenGL features in OpenGL 3.2+
    </description>
    <param name="position" type="vec3" state="POSITION" />
    <param name="modelViewProjectionMatrix" type="mat4" state="MODELVIEW_PROJECTION_MATRIX" />
    <param name="color" type="vec4" state="COLOR" />
    <language name="glsl" version="1.5">
        <bind param="position" program="vp" />
        <bind param="modelViewProjectionMatrix" program="vp" />
        <bind param="color" program="vp" />
        <program name="vp" type="vertex">
            <![CDATA[
// Preprocessor
#version 330 core
// Definitions
// Uniforms
uniform mat4 modelViewProjectionMatrix;
// Attributes
in vec3 position;
in vec4 color;
// Output
out jit_PerVertex {
    flat vec4 color;
} jit_out;
// Library functions
void main() {    
    gl_Position = modelViewProjectionMatrix * vec4(position, 1.);    
    jit_out.color = color;
}
]]>
        </program>
        <program name="fp" type="fragment">
            <![CDATA[
#version 330 core

in jit_PerVertex {
    flat vec4 color;
} jit_in;
out vec4 color;
void main() {
    color = jit_in.color;
}    

]]>
        </program>
    </language>
</jittershader>